A Sumatran tiger comes out of the water in its enclosure during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

A Sumatran tiger bathes in its enclosure during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

A jaguar is pictured in its enclosure during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

Two hippopotamuses reach for water sprayed in their enclosure during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

An American black bear bathes in its enclosure during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

A giraffe tries to reach a branch during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

Two meerkats look into the sun during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

People look at meerkats during a summer day at the Los Angeles Zoo in Los Angeles, California U.S., August 13, 2016. (Photo by Mario Anzuoni/Reuters)

Wildebeests (connochaetes taurinus) jump to cross the Mara river during their migration to the greener pastures, between the Maasai Mara game reserve and the open plains of the Serengeti, southwest of Kenya's capital Nairobi, August 15, 2016. (Photo by Thomas Mukoya/Reuters)

Wildebeests (connochaetes taurinus) cross the Mara river during their migration to the greener pastures, between the Maasai Mara game reserve and the open plains of the Serengeti, southwest of Kenya's capital Nairobi, August 15, 2016. (Photo by Thomas Mukoya/Reuters)

A wildebeest (connochaetes taurinus) and her calf are pictured as they prepare to cross the Mara river during their migration to the greener pastures, between the Maasai Mara game reserve and the open plains of the Serengeti, southwest of Kenya's capital Nairobi, August 15, 2016. (Photo by Thomas Mukoya/Reuters)

Wildebeests (connochaetes taurinus) cross the Mara river during their migration to the greener pastures, between the Maasai Mara game reserve and the open plains of the Serengeti, southwest of Kenya's capital Nairobi, August 15, 2016. (Photo by Thomas Mukoya/Reuters)

Wildebeests (connochaetes taurinus) cross the Mara river during their migration to the greener pastures, between the Maasai Mara game reserve and the open plains of the Serengeti, southwest of Kenya's capital Nairobi, August 15, 2016. (Photo by Thomas Mukoya/Reuters)

Burrowing owls at the Olympic Golf Course on the sixth day of the Rio Olympic Games, Brazil on August 18, 2016. (Photo by David Davies/PA Wire)

Around 100 water voles are being reintroduced into the National Trust’s Malham Tarn in North Yorkshire this weekend. This is the first time the endangered mammals have been seen in the area for 50 years, since the original colony was wiped out by mink in the 1960s. Once a common sight, water vole numbers have dropped by almost 90% in recent years. (Photo by Richard Rayner/North News & Pictures Ltd for National Trust)

A pair of gelada baboons relax in hot weather at the new Gelada Rocks enclosure at Wild Place Project in Bristol, UK on August 16, 2016. The all-male group are settling in after their arrival from a zoo in Zurich, Switzerland. (Photo by Ben Birchall/PA Wire)

Two giraffes stand together in their enclosure at the zoo in Berlin on August 18, 2016. (Photo by Maurizio Gambarini/AFP Photo/DPA)

A female black rhino confronts a herd of elephants at the Moringa waterhole in Etosha national park, Namibia on August 17, 2016. (Photo by Andrew Forsyth/Barcroft Images)

Pierre Thivillon (R), director of the zoological park of Saint-Martin-La-Plaine and his wife Eliane look at Digit, an 18-year-old female gorilla, on August 19, 2016, in Saint-Martin-La-Plaine between Lyon and Saint-Etienne, southeastern France. The zoological park of Saint-Martin-La-Plaine is a shelter for beasts seized by the justice. (Photo by Philippe Desmazes/AFP Photo)

A snow monkey sits by the water on a hot afternoon at the Central Park Zoo on August 18, 2016 in New York City. According to the latest Nasa data, July 2016 was the hottest month in recorded history, beating the record set just 12 months before. (Photo by Spencer Platt/Getty Images)

A seal stays cool in the water on a hot afternoon at the Central Park Zoo on August 18, 2016 in New York City. (Photo by Spencer Platt/Getty Images)

This picture taken on August 18, 2016, shows Gincko, a 14 years old male gorilla, in Saint-Martin-La-Plaine between Lyon and Saint-Etienne, southeastern France.
The zoological park of Saint-Martin-La-Plaine is a shelter for beasts seized by the justice. (Photo by Philippe Desmazes/AFP Photo)

This picture taken on August 18, 2016, shows the Gincko, a 14 years old male gorilla, in Saint-Martin-La-Plaine between Lyon and Saint-Etienne, southeastern France. (Photo by Philippe Desmazes/AFP Photo)

This Aug. 10, 2016, image provided by OET/NautilusLive shows a stubby squid on the ocean floor near Channel Islands National Park west of Los Angeles, Calif. The team of scientists that discovered the cephalopod that is closely related to a cuttlefish is part of a four-month Ocean Exploration Trust expedition to map fault zones and understand ecosystems around them. (Photo by OET/NautilusLive via AP Photo)

A cayman rest on a tree trunk in it's enclosure at the d'Abidjan Zoo, Abidjan, Ivory Coast, 15 august 2016. During the civil war in 2011, Abidjan's only zoo fell into disrepair and many animals died. Now, the facility is getting a makeover, and wants to become a center for conservation excellence in West Africa. (Photo by Legnan Koula/EPA)

Ten-year-old Gorilla Nalani holds her baby in her enclosure at Bioparc zoo in Valencia, eastern Spain, 18 August 2016. Nalani gave birth on 17 August. (Photo by Kai Foersterling/EPA)